Lean body mass is an important determinant of resting and 24-hour energy expenditure. Individuals who suffer spinal cord injuries (SCI) experience a marked loss of muscle mass which may decrease energy expenditure and promote an increase in body fat. This project was designed to test the hypothesis that energy expenditure is decreased in patients with spinal cord injuries as a consequence of their marked muscle atrophy . 24-hour energy expenditure (respiratory chamber), resting metabolic rate (measured by indirect calorimetry) and body composition (dual-energy X-ray absorptiometry (DXA)) were compared in subjects with spinal cord injuries and age-matched able-bodied individuals. 24-hour energy expenditure was lower in 10 males with SCI compared to 59 able-bodied controls (1870+/-73 vs. 2376+/-45 Kcal/24h, p<0.01). After adjusting for differences in fat-free mass, fat mass and age, the resting metabolic rate remained lower in SCI patients than controls (-162 kcal/day, p<0.01) indicating that factors besides the loss of fat-free mass, such as lower sympathetic nervous system activity or a shift to lower oxidative capacity type II muscle fiber may contribute to the lower energy expenditure in SCI patients. Strategies to reduce the excess risk of obesity, diabetes and cardiovascular disease in this population must, therefore, consider the multifactorial nature of the decrease in energy expenditure in this population. This project has been terminated as of the 1997 fiscal year.